The present invention relates generally to the production of semiconductor devices and, more particularly, to semiconductor manufacturing systems including a getter-based gas purifier with a safety device.
Modern semiconductor manufacturing systems use ultrapure gases to produce high density semiconductor devices. One way of providing such ultrapure gases is through the use of a getter-based gas purifier. This type of gas purifier typically includes a getter column which has a vessel containing a bed of getter material. The getter material purifies gas flowing therethrough by adsorbing impurities from the gas.
Getter columns are hazardous because the getter material contained therein is highly reactive with high concentrations of impurities. For example, in the event a high concentration, e.g., a few percent depending on the gas flow rate, of an impurity, e.g., oxygen, is introduced into a getter column containing a known zirconium-based getter material, an exothermic reaction occurs the heat from which may cause melting of the containment wall of the vessel. The containment wall, which is typically formed of stainless steel, may melt at temperatures as low as about 1,000.degree. C. because the getter material contacting the containment wall reacts therewith and forms a eutectic composition. If melting of the containment wall results in the formation of a hole therein, then breach of containment of the getter material occurs, which is potentially catastrophic.
One known getter-based gas purifier for purifying argon includes an alarm device for protecting the getter column from breach of containment of the getter material. This alarm device includes a thermocouple element located three inches below the top of the bed of getter material. Existing getter columns do not have a thermocouple at the bottom of the bed. When a control unit coupled to the thermocouple element measures a temperature of 450.degree. C., which is 50.degree. C. above the normal operating temperature of this getter column, the control unit actuates isolation valves which isolate the getter column, i.e., shut off the flow of gas into and out of the getter column. Unfortunately, the alarm device typically does not stop the flow of high impurity gas into the getter column in time to prevent the getter column from sustaining substantial damage caused by overheated getter material contacting the stainless steel walls of the vessel. Thus, the alarm device does not reliably protect the getter column from breach of containment of the getter material.
In view of the foregoing, there is a need for a safety device for getter-based gas purifiers which reliably protects against breach of containment of the getter material in the event high concentrations of impurities are introduced into a getter column. There is also a need for a semiconductor manufacturing system which includes a getter-based gas purifier having such a safety device so that the fabrication facility in which such system is installed is protected from damage which may result from catastrophic failure of a getter column.